Effect of surgical stress on murine natural killer cell cytotoxicity.

Natural killer cell cytotoxicity (NKCC) against tumors may be important in preventing in vivo solid tumor dissemination. Multiple animal models demonstrate increased rates of tumor dissemination after surgical stress; previously, we have observed that surgical stress impairs murine NKCC. Because of the importance of surgery in the control of solid tumors, it appeared valuable to examine the mechanism underlying surgical stress impairment of NKCC. The results of this study demonstrate that postsurgical suppression of NKCC begins as early as 2 hr after murine hind limb amputation, reaches nadir at 4 days, and does not recover to control level until postoperative day 12. Anesthetic treatment alone does not cause comparable NKCC suppression. The suppression of NKCC accompanied changes in both splenic size and morphology. The immune suppression was observed in multiple compartments including peripheral blood, bone marrow, and spleen. Mixing experiments demonstrated that surgical stress per se generated a suppressor cell population affecting NKCC. The observed suppression apparently required cell-to-cell contact, because supernatants from 4 and 18 hr cultures of suppressor cells did not cause suppression. The observed suppression was prevented by perioperative treatment with the pyrimidinone analog 2-amino-5-bromo-6-phenyl-4-pyrimidinol. These preclinical observations point to the future prospect of NK-specific perioperative immunotherapy that may help prevent possible tumor dissemination from occurring at the time of surgery.